The invention relates to a universal joint or coupling provided with an outer ring having a cavity, an inner ring accomodated in the cavity, and a series of flattened balls which by their round surface are capable of motion in groove-like ball races formed in the cavity and the inner ring, and at the same time during rotation transmit forces from one ring to the other, the flat face of a ball cooperating with the curved surface of the respective ring, the balls being retained by a flexible ball cage.
Such a coupling is described in Dutch patent application No. 79.02092 corresponding to U.S. application Ser. No. 127,809, filed Mar. 6, 1980.
This known coupling is described as being designed such that on the outer surface of the inner ring is mounted a ball-retaining ring supporting four elements which project into the ball races of the inner ring, and on the outer end of the outer ring, over the opening of the cavity of the outer ring, is applied a yielding sealing ring projecting toward the inner ring or the retaining ring.
The present invention seeks to procure a simple coupling design as concerns the means for retaining the balls. For this purpose the coupling pursuant to the invention is characterized in that the balls, over the portion of their spherical surface lying in the space between the groove-like ball races, are enclosed by a flexible annular element known as a ball acge.
The ball cage herein is made of elastic material, as a result of which the balls, which are self-adjusting, i.e., assume the most effective position during loading, are accordingly able to deform the cage slightly. The state of the cage is thus determined exclusively by the self-adjusting balls. In fact, the cage ensures that the balls will not fall out of the coupling and at the same time that the automatic adjustment of the balls will not be hindered or influenced in any way.
Because the cage is made of elastic material it is so flexible that the cage and the entire coupling are very simple to assemble.
It is advantageous if the cage is made of what is known as a solid lubricant, which ensures optimum lubrication of the coupling.
In particular, the coupling pursuant to the invention may be designed such that the cage has the shape of an annular skin of a sphere, the spherical outer surface of which matches the spherical surface of the cavity of the outer ring while the spherical inner surface of the cage is concentric to the spherical outer surface of the cage and matches the spherical outer surface of the inner ring.
The invention will now be explained by means of the drawing, in which a preferred embodiment of the coupling pursuant to the invention is represented.